A tit gives a pied flycatcher information about good nesting spots

The neighbourly relationship between the European pied flycatcher and the great tit provides valuable information about behaviour between the species. Species living in the same area are not only in competition with each other, but also model their behaviour following each other’s example.

FACTS

Diversity of species interactions: a missing key for understanding biodiversity in the changing world

The spearhead project of the research focus area Earth and near-space system and environmental change at the University of Oulu.

Duration 1 January 2017–31 December 2020.

Completed in the Kvantum Institute with funding from Oulu University.

Senior Researcher Jukka Forsman leads the project, and the other participants include one post doc researcher and two doctoral students.

The cooperative partner is James Thorson, National Oceanic Atmosphere Administration (NOAA), Seattle, USA.

At the end of April, when the weather warms up and snow melts away, the great tit chooses its nest.

A couple of weeks later, around Mother's Day in May, the European pied flycatcher arrives at the same nesting area after wintering in Africa.

By then, the tit has already laid its eggs.

The later in the spring the pied flycatcher returns to Finland, the more it models its behavior after the tit. The tit spends the whole year in the same region. It has chosen a nesting site which has plenty of food available and no threat from predators. The tit possesses important information. Photo: Mikko Saari

"We have experimentally proved that the European pied flycatcher, a tropical migratory bird, copies the choices made by the great tit, which is a sedentary bird”, says Senior Researcher and Deputy Director of the Kvantum Institute Jukka Forsman.

The group's findings show that many migratory birds seek areas where there are various tits breeding.

"Since Darwin’s times, the general assumption has been that species using the same resources are in competition with each other. However, our research has amended this impression. There is also positive interaction between different species", says Forsman.

Assumptions regarding the interaction between different bird species are revised.

A real estate broker and an information parasite

Many people had doubts about Jukka Forsman’s plan of attaching symbols to nest boxes.

"At first, I was sniggered at slightly, but now I am proud of the outcome of the experiment," he says.

A triangular symbol was placed by the entrance hole of a tit’s nest box. Next to it, there was an empty box with a circle by its entrance hole.

Two empty nest boxes were placed 25 metres away, one with a triangle, one with a circle.

Most often, the European pied flycatcher chose the box with the triangle – following the tit’s example.

In Jukka Forsman´s experiments the European pied flycatcher most often chose the box with a triangle – following the tit´s example.

"This kind of reasoning is quite an achievement for the bird’s brain," Forsman thinks.

He has also studied how the number of tits’ eggs affects European pied flycatchers’ nesting. In another experiment, moss, hair and plastic eggs imitating tits’ eggs were placed in test nest boxes.

There were 13 eggs in one nest and four in the other one. There was an empty nest box close to both.

"The more eggs the tit had, the more eggs the European pied flycatcher laid in the empty nest. Information about the number of eggs has an effect on how many nestlings the European pied flycatcher has. It deciphers the quality of the nesting place by the number of the tit’s eggs", Forsman states.

The researcher describes how the tit works as an unintentional real estate agent, informing the European pied flycatcher on the quality of the nesting place.

The pied flycatcher, in turn, is an information parasite, taking sneaky peeks at tits’ nests.

The project examines how the changes in habitat affect the relationship between species and the diversity of animal communities.

Following the American model

Jukka Forsman has devoted his whole scientific career to studying the interaction between species, and now he is in charge of a research project nominated as one of the strategic spearhead projects of the Oulu University’s research focus area Earth and near-space system and environmental change.

Diversity of species interactions: a missing key for understanding biodiversity in a changing world explores the interaction between species from the standpoint of diversity.

"The interaction between species is an important factor in shaping biodiversity. It affects the richness and diversity of species,” Forsman says.Something has, however, been missing.

"As yet, there has been no easy-to-use instrument to describe the interactions between species. We now aim to create one."

When Forsman started to take the project forward two or three years ago, he contacted James Thorson, a fish ecologist from the USA, who had just released his own model for statistical analysis. Thorson became excited about the cooperation.

"His model takes in raw data collected from animal communities and ejects a matrix that can be used to assess the interactions between species. We have bird calculation material collected from Finland and France over a period of 40 years, from thousands of bird observation points and relating to more than half a million individuals."

The aim is to calculate an individual interaction index for each community, indicating the different types of interaction and how individual species influence each other.

Environmental changes reflect on the species

Jukka Forsman’s research group has started to enter the existing data to Thorson’s model after a period of training in April.

In addition to creating the actual index, the project will later examine how environmental changes affect it, mirroring their effects on species diversity. European satellite material will be used for this purpose.

“We will analyse rain fall, temperature, land use and human activities. Based on these, we will calculate the degree of interference”, says Forsman.

The third objective relates to the stability of species, which, according to Forsman, is the eternal question of ecology.

The goal of Jukka Forsman´s research is now to create an easy-to-use instrument to describe the interactions between species. Photo: Sanna Häyrynen

"Interactions between species are important in the dynamics of communities. Our goal is to find out how the diversity of interactions affects the species’ ability to resist change or recover after the change."

Forsman points out the importance of estimating how global changes, such as climate change or changes in the living environment, affect interactions between animal species and the diversity of animal communities.

"When living conditions change, everything changes. The animals have to adapt to the new environment and new species in their community."

The project’s basic research will increase the understanding of this issue.